Light(ning) Organ

A light organ (aka color organ) is a device that uses sound to trigger light.  More sophisticated versions of this concept can be found at any club with a dj and lighting rig.  In fact, rather than sound effects, these devices were primarily designed to trigger multi-colored lights by whatever music you put on.  Often these were simple enclosures of lights you put on top of your stereo or on the wall next to your blacklight posters, man.

In spite of its arty origins, all I've really ever wanted to do with a circuit like this is to have it trigger lightning to a thunderous soundtrack.

Selecting a light organ

There are several options to consider when purchasing a light organ:

Trigger method - Can be via:
Channels - The simplest light organs only have one output.  You can connect several lights to this, of course, but a multi-channel organ will usually trigger separate lights based on the different frequencies.  The idea is that the bass frequencies trigger, say, the blue light while the mids do the greens, and the treble range does the reds (or whatever).  Three channels is adequate for lightning, but you can find circuits with up to seven channels.

Wattage - How much power the can circuit handle.  Odds are your application will be something in your home or front yard rather than an arena, but you need the device to be commensurate with the demands you expect to put on it.

The circuit

There are numerous kits available to build your own light organ or you can buy one already assembled at fairly steep prices (i.e., upwards of a hundred vs. a kit that costs less than $20).  I purchased mine (plus the project box I put it in) through Electronic Goldmine.  Here's a link right to the organ.

It took maybe an hour or so to build, probably less if I would have had my soldering iron set out with a convenient place to work at the time.  Maybe two hours total if you count cutting holes in the project box as well at the testing.

The only problem I had with it was that I connected the power cord backwards (i.e., it's a polarized plug), so it didn't work until I realized the flaw and reversed it.

This model has a sensitivity control to get the lights to trigger at just the output you want.  This is really great for lightning since I want the lights to be flickering a lot, meaning the input is rocking on a knife-edge trigger, pulsing back and forth when the trigger voltage is near its peak.

Some circuits also have control over the individual trigger frequencies, which is a nice luxury, but I could see someone ending up spending entirely too much time tweaking the effects to go with their soundtrack.

If you are good with assembling your own circuits, there are dozens of schematics around the web with any number of options.  This is not a terribly complicated device, so you can design your own with the best features of the examples available.

The soundtrack

Here's my "soundtrack."  The numbers at the front of the file names are ostensibly track numbers, but I intentionally went through and wrote this like line numbers in BASIC code (for those children of the '80s who remember this practice).  Note how the sound effects are all "10" lines.  I just inserted mp3s of silence between those.  Sometimes it's just a few seconds of silence, other times it's four minutes.  The idea is not to over-do the thunder but rather to wait until another group of Trick or Treaters is on the front porch before the lightning strikes again.  I even threw in a couple lightning strikes almost back to back just to mess with the kids.

10 Thunder crash 1.mp3
15 Silence - 1 minute.mp3
20 Thunder crash 2.mp3
25 Silence - 3 minutes.mp3
30 Thunder crash 3.mp3
35 Silence - 2 minutes.mp3
37 Silence - 2 minutes.mp3
40 Thunder crash 4.mp3
45 Silence - 1 minute.mp3
50 Thunder crash 5.mp3
55 Silence - 3 minutes.mp3
60 Thunder crash 6.mp3
65 Silence - 2 minutes.mp3
70 Lightning strike with thunder crash 1.mp3
75 Silence - 3 minutes.mp3
80 Lightning strike with thunder crash 2.mp3
85 Silence - 2 minutes.mp3
90 Simulated lightning strike (left to right).mp3
95 Silence - 2sec.mp3
97 Simulated lightning strike (right to left).mp3
99 Silence - 3 minutes.mp3

Another option is to have just randomize the sounds and silence by putting the player on "shuffle."  However, you can sometimes end up with periods of endless thunder or long gaps without and sounds.  I just didn't want to leave things to chance.

Additional ideas

You can similarly devise a soundtrack with alternate spaces of silence to trigger something like:
Also, it's possible to use audio to drive a servo to make animatronics talk by moving the jaw.  There are some tutorials around the web on how to do that, especially with skulls.

Random idea: A circuit driven by speaker voltage could theoretically be used as a two-channel device by simply taking advantage of the fact the audio can be edited in stereo (i.e., pan some sounds hard left/right to trigger only one controller or the other).

Copyright 2011, 2012 the Ale[x]orcist.